Calcium Channel Blockers for Treating Angina

Calcium channel blockers constitute a large class of drugs that are widely used for treating several cardiovascular problems. They are most commonly used today as a first-line treatment for hypertension, but they are also effective in treating angina, supraventricular tachycardia, and hypertrophic cardiomyopathy. In general, the calcium channel blockers are well-tolerated, but there are certain side effects that need to be watched out for.

Overview

Calcium channel blockers prevent calcium from entering into the heart muscle cells, and into the smooth muscle cells that cause blood vessels to constrict. By reducing calcium influx, calcium channel blockers cause these muscle cells to “relax.” This relaxing effect results in the dilation of blood vessels, and a reduced force of contraction of the heart muscle.

Some calcium channel blockers also slow the sinus node and the rate at which the heart's electrical impulse travels through the AV node. These “electrical effects” of calcium blockers make them useful in treating some arrhythmias.

All the effects of calcium blockers (blood vessel dilation, reduction in heart muscle contraction, and slower heart rate) reduce the amount of oxygen required by the heart muscle.

Reducing cardiac oxygen demand helps to prevent cardiac ischemia (oxygen starvation), even when blood flow through the coronary arteries is partially blocked by an atherosclerotic plaque. In people who have stable angina, calcium blockers usually increase the amount of exercise they can perform before they experience angina. Calcium blockers can be especially useful in people with Prinzmetal’s angina (coronary artery spasm) since they can directly reduce spasm of the coronary arteries.

Types

There are many calcium blockers on the market, and they are not all alike. There are three general types of widely used calcium blockers:

• The dihydropyridines. The drugs nifedipine (Procardia, Adalat), nicardipine (Cardene), felodipine (Plendil), and amlodipine (Norvasc), are called the dihydropyridines. These drugs cause significant dilation of blood vessels and relatively little effect on the heart muscle and heart rate. They are most useful for treating hypertension.
• Verapamil. Verapamil (Calan, Covera, Isoptin, Verelan) affects the heart muscle and is particularly effective in slowing the heart rate, but has little effect on blood vessels. It is not very useful for hypertension but is quite good for angina and cardiac arrhythmias.
• Diltiazem. Diltiazem (Cardizem, Dilacor, Tiazac) has modest effects on both the heart muscle and the blood vessels. It tends to be tolerated better than most other calcium blockers

Usage

Angina: All the calcium blockers have been used for treating angina. However, the most commonly used for this purpose are the longer-acting forms of diltiazem and verapamil, amlodipine, or felodipine.

Nifedipine, especially its short-acting forms, should generally be avoided in people with angina since the pronounced blood vessel dilation produced by this drug can increase in adrenaline, leading to a more rapid heart rate, and consequently an increase in cardiac oxygen requirements. So short-acting nifedipine can actually worsen cardiac ischemia.

In general, while calcium blockers are useful for relieving angina, they are considered to be inferior to beta-blockers. Current recommendations for using calcium blockers for the treatment of angina are:

• Calcium blockers should be tried in patients who cannot tolerate beta-blockers.
• Calcium blockers should be added to beta-blockers in patients who have insufficient relief of symptoms with beta-blockers.

Hypertension: The dihydropyridine calcium blockers are quite useful for treating hypertension and are often used as first-line therapy for Stage I hypertension.

Supraventricular arrhythmias: Calcium blockers (especially verapamil) partially blocks the function of the AV node and therefore is often quite useful in treating the supraventricular arrhythmias that rely on the AV node in order to persist. In particular, AV nodal reentrant tachycardia (the most common kind of supraventricular arrhythmia) can often be controlled with verapamil therapy. 

Hypertrophic cardiomyopathy: Calcium blockers can be used to help reduce the “stiffness” of the left ventricle in people with hypertrophic cardiomyopathy, and in this way can reduce symptoms.

Side Effects

Common most side effects of the dihydropyridine group of calcium channel blockers include headache, dizziness, flushing, and foot and ankle swelling.

The most common side effect of both verapamil and diltiazem is constipation, which can occur in up to 25% of people treated with these drugs. These non-dihydropyridine calcium blockers can also cause bradycardia (slow heart rate), and, because they reduce the force of contraction of the heart muscle, they can lower the cardiac output. They should be used with caution (if at all) in patients with heart failure.

A Word From Verywell

The calcium channel blockers are widely used in treating a variety of cardiovascular disorders. While they are generally well-tolerated, precautions need to be taken to avoid potentially serious side effects.